\begin{frame}
  \frametitle{Definition \hfill(1/2)}
  \setbeamercovered{dynamic}
  \begin{outline}
    \1 The three elemental rotations may be extrinsic (rotations about the axes xyz of the original coordinate system, which is assumed to remain motionless), or intrinsic 
(rotations about the axes of the rotating coordinate system XYZ, solidary with the moving body, which changes its orientation with respect to the extrinsic frame after each 
elemental rotation)
    \1 Euler angles are typically denoted as $\alpha$, $\beta$, $\gamma$ or $\psi$, $\theta$, $\phi$/$\varphi$. Different authors may use different sets of rotation axes to define
      Euler angles, or different names for the same angles
    \1 \textcolor{blue}{Any discussion employing Euler angles should always be preceded by their definition}
    \1 Without considering the possibility of using two different conventions for the definition of the rotation axes (intrinsic or extrinsic), there exist twelve possible 
sequences of rotation axes, divided in two groups:
    \2 Proper Euler angles (z-x-z, x-y-x, y-z-y, z-y-z, x-z-x, y-x-y)
    \2 Tait–Bryan angles (x-y-z, y-z-x, z-x-y, x-z-y, z-y-x, y-x-z)
  \end{outline}
\end{frame}
